Maybe the example would help to describe the expression I am looking for:

Say - a sub-par school or organization makes a promotional video, whereby they make the school look way better than it really is. They accomplished this by interviewing a few successful students, showing only the best parts of the school/classes, picking a few angles, and omitting 80% of what really represents the true situation.

I have heard the following expression, but not sure whether it's appropriate, or even phrased correctly:

Turn chicken into a chicken soup.

EDIT: actually the expression was

Make chicken salad out of chicken $#!%"

coined by Brock Lesnar. Obviously it's less befitting than others mentioned on the thread.

One common idiom is "make a mountain out of a molehill", however the underlying implication of that is "make a problem bigger than it really is", which is kind of the opposite of what you are looking for.

Another common idiom is "putting lipstick on a pig", which means make something that is really bad seem to look a lot better. That might be a good fit for you.

As to the chicken soup one -- I've never heard that expression, Google hasn't either.

You should probably put the molehill one after the lipstick one, or take it out altogether, then.
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DanielSep 2 '11 at 22:04

To put lipstick on a pig is very much an Americanism that's only shot to prominence in the last couple of decades. As a Brit, perhaps I shouldn't comment, but I think it's almost exclusively used by Texans and politicians.
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FumbleFingersSep 2 '11 at 22:15

I don't think it is exclusive to either Texans or politicians, although recent political events brought it to the fore. I have heard it a lot in all sorts of contexts. I'll grant you though that I don't remember hearing it much in the UK. Interestingly, the person I remember using it most was a Belorussian I used to work with. Which doesn't prove anything of course, but is nonetheless a "strange but true."
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Fraser OrrSep 2 '11 at 22:19

Well, I did say that as a Brit I probably really shouldn't comment. We only hear it from US politicians & pundits on the news. So I doubt it'll ever "hit the streets" on this side of the pond, because those are the last kind of people users of new slang expressions would want to emulate.
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FumbleFingersSep 3 '11 at 12:21

In the song Things Are Seldom What They Seem in the operetta HMS Pinafore, there are the lines:

Gild the farthing if you willYet it is a farthing still.

I had always assumed this referred to a standing expression, but just now I wasn't able to find any other references to gilding the farthing, other than ones explicitly referencing that song. There does appear to have been a 1963 book by Brian Almond called Gild the Brass Farthing.

An historical reference or metaphor would be a Potemkin village. These were false village façades (think Western movie sets) that were, according to legend, set up by Grigory Potemkin to impress the Empress Catherine. Generally viewed as fable, you’ll still hear the reference occasionally.

It occurs to me that a less colloquial term would be self-aggrandizement. The OED just has it as “the action or process of promoting oneself as being powerful or important”, but thefreedictionary.com supports my feeling that there is a connotation of exaggeration:

the act or practice of enhancing or exaggerating one’s own importance, power, or reputation.

(Sorry I didn’t put that in my earlier post; it’s been on the tip of my tongue for three days.)